Factorial design optimization and in vivo feasibility of poly(ε-caprolactone)- micro- and nanofiber based small diameter vascular grafts

Because of the severe increase of mortality by cardiovascular diseases, there has been rising interest among the tissue-engineering community for small-sized blood vessel substitutes. Here we present small diameter vascular grafts made of slow degradable poly(epsilon-caprolactone) nanofibers obtained by electrospinning. The process was optimized by a factorial design approach that led to reproducible grafts with inner diameters of 2 and 4 mm, respectively. Fiber sizes, graft morphology, and the resulting tensile stress and tensile strain values were studied as a function of various parameters in order to obtain optimal vascular grafts for implantation after gamma-sterilization. The influence of polymer concentration, solvent, needle-collector distance, applied voltage, flow rate, and spinning time has been studied. Consequently, an optimized vascular graft was implanted as an abdominal aortic substitute in nine rats for a feasibility study. Results are given following up a 12-week implantation period showing good patency, endothelization, and cell ingrowth

Mechanical Evaluation of Hydrogel–Elastomer Interfaces Generated through Thiol–Ene Coupling

The formation of hybrid hydrogel–elastomer scaffolds is an attractive strategy for the formation of tissue engineering constructs and microfabricated platforms for advanced in vitro models. The emergence of thiol–ene coupling, in particular radical-based, for the engineering of cell-instructive hydrogels and the design of elastomers raises the possibility of mechanically integrating these structures without relying on the introduction of additional chemical moieties. However, the bonding of hydrogels (thiol–ene radical or more classic acrylate/methacrylate radical-based) to thiol–ene elastomers and alkene-functional elastomers has not been characterized in detail. In this study, we quantify the tensile mechanical properties of hybrid hydrogel samples formed of two elastomers bonded to a hydrogel material. We examine the impact of radical thiol–ene coupling on the crosslinking of both elastomers (silicone or polyesters) and hydrogels (based on thiol–ene crosslinking or diacrylate chemistry) and on the mechanics and failure behavior of the resulting hybrids. This study demonstrates the strong bonding of thiol–ene hydrogels to alkene-presenting elastomers with a range of chemistries, including silicones and polyesters. Overall, thiol–ene coupling appears as an attractive tool for the generation of strong, mechanically integrated, hybrid structures for a broad range of applications

Factorial design optimization and in vivo feasibility of poly(ε-caprolactone)- micro- and nanofiber based small diameter vascular grafts

Because of the severe increase of mortality by cardiovascular diseases, there has been rising interest among the tissue-engineering community for small-sized blood vessel substitutes. Here we present small diameter vascular grafts made of slow degradable poly(epsilon-caprolactone) nanofibers obtained by electrospinning. The process was optimized by a factorial design approach that led to reproducible grafts with inner diameters of 2 and 4 mm, respectively. Fiber sizes, graft morphology, and the resulting tensile stress and tensile strain values were studied as a function of various parameters in order to obtain optimal vascular grafts for implantation after gamma-sterilization. The influence of polymer concentration, solvent, needle-collector distance, applied voltage, flow rate, and spinning time has been studied. Consequently, an optimized vascular graft was implanted as an abdominal aortic substitute in nine rats for a feasibility study. Results are given following up a 12-week implantation period showing good patency, endothelization, and cell ingrowth